Bio 4th Form BIG

What are enzymes?

- Enzymes are proteins that act as biological catalysts to speed up the rate of reaction without being changed or used up in a reaction.

- They are biological molecules because they are made in cells.

- Enzymes are necessary to all living organisms as they maintain reaction speeds of all metabolic reactions at a rate that can sustain life.

- e.g. if we didn't produce digestive enzymes, digestion would take much longer.

Mechanism of enzyme action

- Enzymes and substrates randomly move about in a solution

- When an enzyme and its complementary substrate randomly collide, an enzyme-substrate complex forms

- A product forms from the substrate which is then released from the active site. The enzyme is unchanged and will go on to catalyse further reactions

Factors that affect enzyme action

- Temp

- pH levels

How does temperature affect enzyme activity?

- Enzymes are proteins determined by amino acids that are held together by bonds.

- The shape of the protein is important to ensure the substrate actually fits into the enzymes.

- Enzymes work best at optimum temp -> around 37°C in human body

- Heating to high temps will break the bonds that hold the enzyme and it will lose its shape -> denaturation

- increasing the temp towards optimum temp increases the activity of the enzymes as the more kinetic energy the molecules have, the faster the move -> increases no. of collisions w substrates.

- Low temps don't denature enzymes, just make them work slower due to low kinetic energy.

How does pH affect enzyme action?

- The optimum pH for enzymes is 7

- Enzymes produced in alkaline conditions e.g. duodenum, have a higher optimum pH of 8 or 9.

If the pH is too high or too low:

- Bonds that hold the amino acid chains to make the protein can be destroyed.

- This changes the shape of the active site -> substrate can't fit

- Reduces rate of activity

- Moving too far from the optimum pH will cause the enzyme to denature + activity will stop.

How do you test for glucose?

- Add Benedict's solution to the sample solution in a test tube.

- Heat in a boiling water bath for 5 mins.

- Take the test tube out and observe the colour.

- A positive test will show a colour change from blue to brick red.

How do you test for starch?

- We use iodine solution to test for the presence or absence of starch in a food sample.

- Add drops of iodine solution to the food sample.

- A positive test will show a colour change from orange/brown to blue/black.

How do you test for protein in a food sample?

- Add drops of Biuret solution to the food sample.

- A positive sample will change colour from blue to purple.

How do you test for lipids?

- Mix the food sample with 4cm3 of ethanol then shake.

- Allow time for the sample to dissolve in the ethanol.

- Strain the ethanol solution into another test tube.

-Add the ethanol solution to an equivalent volume of cold distilled water.

- A positive test will show a cloudy emulsion forming.

What is the Vena Cava?

The main vein returning blood to the heart

What is the Renal Vein?

Takes filtered blood away from kidneys

What is the Aorta?

The main artery supplying oxygenated blood to body

What is the Renal Artery?

Brings blood containing waste to the kidneys

What is the urethra?

Carries urine out of the body

What is the ureter?

Carries urine to the bladder

What is the bladder?

A muscular sac that stores urine

What is the sphincter muscle?

Muscle that keeps the bladder closed

What is the Medulla?

Pyramid shaped areas near the middle of the kidney

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What is a Nephron?

A tiny filtration unit where urine is produced

What is the main function of the kidneys?

To get rid of waste such as:

- Salt

- Excess water

- Excess urea

Why is it important to remove waste products?

- Urea because it is toxic

- Water because of its osmotic effect

- Excess salt (mineral ions) because of its osmotic effect

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Adaptations to do with nephrons

- Animals that need to conserve water, e.g. camels have longer loops of Henlé

- Animals that live near bodies of water have shorter loops of Henlé

What happens in Ultrafiltration?

- High blood pressure in glomerulus

- All small molecules forced out of the blood through pores into Bowman's Capsule

- Large molecules stay in the blood

- Results in a filtered liquid containing small molecules

What happens in Selective Reabsorption?

- Useful small molecules e.g. glucose, amino acids, salt + water are reabsorbed into the blood

- Occurs in Proximal Convoluted Tubule

- Water moves by osmosis while others by diffusion or active transport

- ATP energy needed for active transporte so cells in tubule have lots of mitochondria.

- Filtrate moving from proximal convoluted tubule to the loop of Henlé only contains water, some salt and urea

What is ADH?

- Stands for Antidiuretic Hormone

- Made in the pituitary gland in the brain when we are thirsty

- Travels from the pituitary gland to the kidneys through the bloodstream

- Makes the collecting ducts more permeable to water so more water is reabsorbed into the bloodstream when we are thirsty

- Makes urine very concentrated

Where is blood water level adjusted by the nephrons?

- Water is reabsorbed into the blood in Proximal Convoluted Tubule, loop of Henlé + collecting ducts

- Adjustments to water reabsorption are made in collecting ducts

What happens during osmoregulation when we are dehydrated?

- Blood is more concentrated when we are dehydrated.

- This is detected by osmoreceptors in the hypothalamus.

- Osmoreceptors signal to the pituitary gland to make more ADH.

- ADH travels via bloodstream to the collecting ducts + makes them more permeable to water.

- Allows more water to be reabsorbed into the bloodstream.

- Minimises dehydration in the body.

What is negative feedback?

A response to a change in the body that counteracts or opposes the initial change.

What are the seven food groups?

- Carbohydrates

- Proteins

- Fats

- Vitamins

- Minerals

- Fibre

- Water

What is digestion?

The break down of large insoluble molecules into smaller soluble molecules

What is the function of glucose

An energy source used in respiration

What is a source of glucose?

Fruits

What is the function of starch?

Glucose storage -> broken down into glucose for respiration

What is a source of starch?

Bread

What are the functions of proteins?

- Needed to maintain cell function

- Growth and repair of cells and tissues

What is a source of protein?

Chicken

What is the function of Lipids?

Long term energy storage

What are some sources of Lipids?

Butter, milk, nuts

What is the function of Fibre?

- For plants -> makes up plant cell wall

- Humans -> keeps the digestive system healthy and prevents constipation

What is a source of fibre?

Vegetables

What is the function of minerals?

To make healthy bones and blood

What are some sources of Minerals?

Milk and meat

What is the function of Vitamins?

To take part in important reactions in the body

What are some sources of Vitamins?

Carrots (Vit A), citrus (Vit C), milk (Vit D)

What is the function of water?

To transport substances around the body and replace lost water

What are some sources of water?

Fruit and vegetables

What is the food test for glucose?

- Add Benedict's solution

- when heated, the colour will change from grey to red if glucose is present

What is the food test for starch?

- Use iodine

- If starch is present the colour will change from brown to blue/black

What is the food test for protein?

- Use Biuret's

- If protein is present, the colour will change from blue to purple

What is a balanced diet?

The right ratio of different food groups, providing the body with all essential foods.

What are the symptoms of being underweight?

- Tiredness

- Weak and dizzy

- Loss of fat + muscle tissue

What are the symptoms of being overweight?

- Increase in weight

- High blood pressure

- Heart symptoms

What are deficiency diseases?

Disease caused by a lack of a nutrient food group

What is the mouth?

The starting point of digestion

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What is the tongue?

A muscle that mixes food with saliva

What is the function of the oesophagus ?

Transport of food to stomach

What is the function of the stomach?

Storage and digestion of food

What is the function of the duodenum?

Main digestion of food

What is the function of the pancreas?

Secretes digestive juices and enzymes

What is the function of the gall bladder?

Site if bile salt storage

What is the function of the liver?

Site if bile salt production

What is the function of the ileum?

Main absorption of nutrients

What is the function of the large intestine?

Absorption of water

What is the function of the rectum?

Temporary storage of faeces

What is the function of the anus?

Defecation

What is peristalsis?

A series of wave-like muscle contractions that moves food along the digestive system

How are foods absorbed into the bloodstream?

- The ileum is lined by thousands of villi

- The nutrients are absorbed into the bloodstream by diffusion

Why can humans not take in oxygen via diffusion?

Humans have a small SA/vol ratio -> diffusion across their surfaces wouldn't be efficient.

What happens during inhalation?

- Diaphragm flattens as it contracts

- External intercostal muscles contract -> rib case moves up and out

- Thorax volume increase

- Pressure in thorax is lowered

- Atmospheric pressure forces air into lungs

- Lungs expand as pressure equalises

What happens to the diaphragm during exhalation?

- Diaphragm relaxes

- Intercostal muscles contract

- Thorax volume decreases

- Pressure in thorax increases

- Air is forced out of lungs until air pressure inside and outside chest is equal

Short term effects of smoking on the body

- Less oxygen travels to the brain

- Stained teeth + smelly breath

- More coughing + colds

- Less oxygen to lungs -> tiredness, dizziness + increased heart rate

- Stained fingers

Long term effects of smoking

- Stroke

- Vision loss

- Gum disease + tooth loss

- Mouth + throat cancer

- Oesophagus cancer

- Emphysema

- Lung cancer

- Chronic bronchitis

- Stomach cancer

- Pancreatic cancer

- Decreased fertility

- Heart disease

- Peripheral vascular disease

Effects of tar on the human body

- Lung cancer -> contains carcinogens

- Emphysema -> chemicals in tar

- Damaged alveoli -> decreased SA/vol ratio

- Chronic bronchitis / lung infections -> cilia in bronchitis paralysed

Effects of nicotine on human body

- Addiction

-> Addictive substances in cigarettes stimulates neurotransmitter release in brain leading to cravings

- Strokes and heart attacks -> constricts arteries, reducing blood flow around the body

Effects of carbon monoxide on the human body

- Tiredness, dizziness, increased heart rate

-> binds irreversibly to have ogle in instead of oxygen

-> reduces the amount of oxygen going to body cells

-> less respiration happens -> less energy

- Reduction in birth mass -> foetus gets less oxygen

-> less respiration therefore less energy for growth

Tidal Volume definition

The volume of air breathed in and out with each breath at rest

Vital Capacity

The maximum volume of air that can be breathed in and out

Inspiratory reserve volume

The maximum volume of air that can be inhaled beyond tidal volume

Expiratory reserve volume

The maximum volume of air that can be exhaled beyond tidal volume

Residual Volume

The volume of air remaining in the lungs after maximal exhalation

Total Lung Capacity

The volume of the lungs at maximal inflation

How does gas exchange work?

- Deoxygenated blood travels through the heart to the lungs via the pulmonary artery

- The blood flows from the pulmonary artery to the blood capillary surrounding the alveolus

- Oxygen diffuses from the alveoli into the blood capillaries

- Because we breathe in oxygen, the alveoli always have a high concentration of oxygen for diffusion

- Carbon dioxide diffuses from the blood capillaries to the alveoli to be exhaled

- Blood travels back to the heart through the pulmonary vein.

What is the function of the circulatory system?

To pump blood around the body -> to move materials to and from cells

-> to help fight diseases

-> to help stabilise body temp

What is transported in the blood?

- Nutrients

- Waste

- Hormones

What is the use of the coronary artery?

To bring oxygen to the heart muscle

What happens if the coronary artery is blocked?

- Blood supply to the area of cardiac muscle is cut off

- Less oxygen and glucose reaches the muscle cells

- The area of heart muscle cannot respire aerobically -> dies

- Results in heart pain or heart attack

What is cardiac output?

- The volume of blood pumped out of the heart in a minute

- Can be increased by increasing the heart rate or stroke volume -> volume per heart beat

Heart phases in order

- Diastole

- Atrial Systole

- Ventricular Systole

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What happens in atrial systole?

- Atria contracts

- Only AV valves open

- Blood flows into the ventricle

- Pressure increases due to atrial contraction

What happens in ventricular systole?

- Ventricles contract

- Only pocket valves open

- Blood flows into arteries

- Pressure increases due to ventricular contraction

Artery info

- Blood flows from the heart to the body

- High blood pressure

- Carries oxygenated bright red blood

- Has a thick elastic + muscle wall

- Small lumen -> keeps pressure high

- No valves

- 0.5 - 20mm

Vein info

- Transports blood from body to heart

- Low pressure

- Carries deoxygenated, deep purple/red blood

- Has a thin elastic + muscle wall

- Large lumen -> keeps pressure low

- Has valves

- 0.5 - 20mm

Capillary info

- Transports blood from arteries to veins I'm capillary beds within organs

- Medium pressure

- Oxygenated to deoxygenated blood

- Has a very thin wall + very small lumen

- No valves

- 7 micrometers

Composition of blood

- Blood plasma is a yellow liquid.

- It consists of 90% water and carries dissolved substances e.g. glucose and waste

- White blood cells

-> phagocytes engulf pathogens and digest them. Lymphocytes produce antibodies which travel in the blood and attach to antigens

What is a capillary bed?

A vast network of capillaries within a tissue